| Abstract |
Designing a high voltage, very fast switch for chopping the 380 V mains at frequency in excess of 20 KHz and current in order of 50 A is not very easy. The well known circuits and components currently used in industrial applications can be no longer used at these frequencies. New circuits must be developped including the latest improvements. In the first part of this paper, a review of the specific behavior of high voltage bipolar transistors and Darlingtons is done. Particular problems like dynamic saturation, RBSOA and current derating are discussed. Solutions and examples of circuits are given. The second part of the paper is dedicated to the improvements of classical solutions using open emitter control. Problems encountered with open emitter controlled high voltage Darlingtons are discussed. Cautions for use and examples of circuits are also given. |
